To better understand the fracture behavior of TA15 titanium alloy during hot forming, three groups of experiments were conducted to investigate the influence of deformation temperature, strain rate, initial microstruc...To better understand the fracture behavior of TA15 titanium alloy during hot forming, three groups of experiments were conducted to investigate the influence of deformation temperature, strain rate, initial microstructure, and stress triaxiality on the fracture behavior of TA15 titanium alloy. The microstructure and fracture surface of the alloy were observed by scanning electronic microscopy to analyze the potential fracture mechanisms under the experimental deformation conditions. The experimental results indicate that the fracture strain increases with increasing deformation temperature, decreasing strain rate, and decreasing stress triaxiality. Fracture is mainly caused by the nucleation, growth, and coalescence of microvoids because of the breakdown of compatibility requirements at the α/β interface. In the equiaxed microstructure, the fracture strain decreases with decreasing volume fraction of the primary α-phase(αp) and increasing α/β-interface length. In the bimodal microstructure, the fracture strain is mainly affected by α-lamella width.展开更多
Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation.Spectral measurement results showed that as the deposition temperature increased from 10...Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation.Spectral measurement results showed that as the deposition temperature increased from 100°C to 300°C,the transmittance of the films in the wavelength range from 350 nm to 2100 nm decreased.After annealing in air at 500°C,the transmittance significantly increased and approached that of uncoated fused quartz.Based on the Tauc plot method and Mott-Davis-Paracrystalline model,the optical band gap of Ge films was calculated and interpreted.The difference in optical band gap reveals that the deposition temperature has an effect on the optical band gap before annealing,while having little effect on the optical band gap after annealing.Furthermore,due to oxidation of Ge films,the optical band gap was significantly increased to^5.7 eV after annealing.展开更多
The infuence of(Li,Ce)doping on the electrical properties of bismuth layer Sr_(2)Bi_(4)Ti_(5)O_(18)[abbreviated to SBTi-(Li,Ce)_(x/2)]ceramics was investigated.X-ray difraction analy sisshowed that all the ceramic sam...The infuence of(Li,Ce)doping on the electrical properties of bismuth layer Sr_(2)Bi_(4)Ti_(5)O_(18)[abbreviated to SBTi-(Li,Ce)_(x/2)]ceramics was investigated.X-ray difraction analy sisshowed that all the ceramic samples were'single-phase compounds.The(Li,Ce)modification sig.nificantly decreased the dielectric loss of Sr,Bi,Ti,O 1s ceramics and greatly improved the piezo-electric activity.At x/2=0.0125,the SBTi-(Li,Ce)_(x/2)ceramics exhibited the excellent propertieswith high remnant polarization(Pr=9.3μc/cm^(2))and high Curie temperat ure(T_(c)=299°C).Meanwhijle,the SBTi-(Li,Ce)_(0.0125)ceramics had the largest piezoelectric constant(d_(33)=26 pC/N).Theresultsshowed that the SBTi-(Li,Ce)_(x/2)ceramic was a promisinglead-free piezoelectric mat erial.展开更多
基金financially supported by the Research Fund for the Doctoral Program of Higher Education of China(No.20120006110017)
文摘To better understand the fracture behavior of TA15 titanium alloy during hot forming, three groups of experiments were conducted to investigate the influence of deformation temperature, strain rate, initial microstructure, and stress triaxiality on the fracture behavior of TA15 titanium alloy. The microstructure and fracture surface of the alloy were observed by scanning electronic microscopy to analyze the potential fracture mechanisms under the experimental deformation conditions. The experimental results indicate that the fracture strain increases with increasing deformation temperature, decreasing strain rate, and decreasing stress triaxiality. Fracture is mainly caused by the nucleation, growth, and coalescence of microvoids because of the breakdown of compatibility requirements at the α/β interface. In the equiaxed microstructure, the fracture strain decreases with decreasing volume fraction of the primary α-phase(αp) and increasing α/β-interface length. In the bimodal microstructure, the fracture strain is mainly affected by α-lamella width.
基金supported by the National Key Research and Development Project of China (No. 2016YFE0104300)
文摘Ultrathin Ge films with thickness of about 15 nm at different deposition temperatures were prepared by electron beam evaporation.Spectral measurement results showed that as the deposition temperature increased from 100°C to 300°C,the transmittance of the films in the wavelength range from 350 nm to 2100 nm decreased.After annealing in air at 500°C,the transmittance significantly increased and approached that of uncoated fused quartz.Based on the Tauc plot method and Mott-Davis-Paracrystalline model,the optical band gap of Ge films was calculated and interpreted.The difference in optical band gap reveals that the deposition temperature has an effect on the optical band gap before annealing,while having little effect on the optical band gap after annealing.Furthermore,due to oxidation of Ge films,the optical band gap was significantly increased to^5.7 eV after annealing.
基金supported by the Ph.D.Programs Foundation of Shandong Province of China(No.BS2010CL010)National Natural Science Foundation of China(No.50702068).
文摘The infuence of(Li,Ce)doping on the electrical properties of bismuth layer Sr_(2)Bi_(4)Ti_(5)O_(18)[abbreviated to SBTi-(Li,Ce)_(x/2)]ceramics was investigated.X-ray difraction analy sisshowed that all the ceramic samples were'single-phase compounds.The(Li,Ce)modification sig.nificantly decreased the dielectric loss of Sr,Bi,Ti,O 1s ceramics and greatly improved the piezo-electric activity.At x/2=0.0125,the SBTi-(Li,Ce)_(x/2)ceramics exhibited the excellent propertieswith high remnant polarization(Pr=9.3μc/cm^(2))and high Curie temperat ure(T_(c)=299°C).Meanwhijle,the SBTi-(Li,Ce)_(0.0125)ceramics had the largest piezoelectric constant(d_(33)=26 pC/N).Theresultsshowed that the SBTi-(Li,Ce)_(x/2)ceramic was a promisinglead-free piezoelectric mat erial.
